Acknowledgements

We are grateful to all the past and present members of CarbFix that made the project possible. We furthermore greatly acknowledge the funding granted to the project. During the pilot phase of CarbFix, the project received funding by the European Commission through the projects CarbFix (EC coordinated action 283148), Min-GRO (MC-RTN-35488), Delta-Min (PITN-GA-2008-215360), and CO2-REACT (EC Project 317235). Nordic fund 11029-NORDICCS; the Icelandic GEORG Geothermal Research fund (09-02-001); and the U.S. Department of Energy under award number DE-FE0004847. After commencing its industrial scale operations, CarbFix has further received grants from the European Union's Horizon 2020 research and innovation program under grant agreements No. 764760 (CarbFix2) and 764810 (S4CE).

A brief history of CarbFixSigurdur R. Gíslasona, Hólmfrídur Sigurdardóttirb, Edda Sif Aradóttirb and Eric H. Oelkersa,c,d

aInstitute of Earth Sciences, University of Iceland, Sturlugötu 7, 101 Reykjavík, Iceland. bReykjavík Energy, Bæjarháls 1, 110 Reykjavík, Iceland.cGéosciences Environnement Toulouse (GET) - CNRS, 14 Avenue Édouard Belin, 31400 Toulouse, France. dEarth Sciences, UCL, Gower Street, London, United Kingdom.

ABSTRACTThe pilot phase of the CarbFix project ran for over a decade and consisted of the training of students, creating the scientific basis for the fixation of carbon dioxide in the subsurfacethrough the in-situ carbonation of basalts, and the demonstration of this technology by fixing approximately 200 tons of injected CO2 as carbonate minerals during 2012 and 2013. Overthe course of this effort, numerous parts of this project have been reported in scientific articles, but a number of challenges including that of separating CO2 gas from a H2S-rich effluentgas, the clogging of the original CarbFix injection well and the damage to the project’s gas pipe by a third party that eventually shut down the project’s pilot phase, have yet to bedetailed in the scientific literature. This brief poster reviews the CarbFix timeline over the past 12 years, describing some of these challenges.

References[1] Gislason S.R., and E.H. Oelkers. “Carbon Storage in Basalt” Science 344 (2014): 373−374. [2] Snæbjörnsdóttir S.Ó., E.H. Oelkers, K.G. Mesfin, E.S.P. Aradottir, K. Dideriksen, I. Gunnarsson, E. Gunnlaugsson, J. Matter, M. Stute, and S.R. Gislason. “The chemistry and saturation states of subsurface fluids during the in situ mineralization of CO2 and H2S at the CarbFix site in SW-Iceland” International Journal of Greenhouse Gas Control 58 (2017): 371−380. [3] Snæbjörnsdóttir S.Ó., S.R. Gislason, I.M. Galeczka, and E.H. Oelkers. “Reaction path modelling of in-situ mineralisation of CO2 at the CarbFix site at Hellisheidi, SW-Iceland” Geochimica et Cosmochimica Acta 220 (2018): 348−366. [4] Matter J.M., M. Stute, S.Ó. Snæbjörnsdóttir, E.H. Oelkers, S.R. Gislason, E.S.P. Aradottir, B. Sigfusson, I. Gunnarsson, H. Sigurdardottir, E. Gunnlaugsson, G. Axelsson, H.A Alfredsson, D. Wolff-Boenisch, K.G. Mesfin, D.R. Fernandez, J. Hall, K. Dideriksen, and W.S. Broecker. “Rapid carbon mineralization for permanent and safe disposal of anthropogenic carbon dioxide emissions” Science 352 (2016): 1312−1314. [5] Gunnarsson, I., Aradóttir, E.S., Oelkers, E.H., Clark, D.E., Arnarson, M.Þ., Sigfússon, B., Snæbjörnsdóttir, S.Ó., Matter, J.M., Stute, M., Júlíusson, B.M. and Gíslason, S.R. “The rapid and cost-effective capture and subsurface mineral storage of carbon and sulfur at the CarbFix2 site.” International Journal of Greenhouse Gas Control 79 (2018), 117–126.

Figure 2. Objective and work packages of the pilot phase of the CarbFix project.

Figure 4. (A) Conventional injection of supercritical CO2 into sedimentary basin with impermeable cap rock. (B).Injection of CO2-charged water into basaltic rocks at the CarbFix pilot injection site at Hellisheidi, Iceland.Superimposed on a) and b) are the potential dissolution and precipitation reactions occurring after injection, assumingthat porous sedimentary basins are dominated by quartz sandstone (modified from [1]). Mass balance calculations,based on the recovery of non-reactive tracers co-injected into the subsurface together with the acid-gases, confirmedthat more than 95% of the CO2 injected into the subsurface was mineralised within two years, and essentially all of theinjected H2S was mineralised within four months of its injection [2-4].

Figure 3. The pilot gas capture plant, with the scrubber tower (right), deaerator(lowest column in the middle) and the distillation column, the tallest column on theleft. Photo: Ingvi Gunnarsson.

Figure 5. A brief timeline for CarbFix. In the pilot phase of CarbFix, pure CO2 and a CO2-H2S gas mixture were injected at350 m depth and 20-50 °C in 2012. In 2014 a CO2+H2S gas mixture was continuously injected below 700 m depth andinto a hotter part of the geothermal system (>250°C). The annual capacity of this up-scaled injection was ca. 15,000tons of CO2-H2S gas mixture in 2017. Direct air capture (DAC) started in 2017.

Figure 1. Members of the CarbFix scientific steering committee together with thePresident of Iceland at Hellisheiði Geothermal Power Plant in September 2009. Fromthe left: Dr Einar Gunnlaugsson, Dr Sigurdur Gíslason, President of Iceland Dr ÓlafurRagnar Grímsson, Dr Wally Broecker and Dr Eric Oelkers. Photo: Sigfús MárPétursson.

Production well Injection well

Separator Power plant

Brine

Steam

CondensateGeothermal

gas

Cleaned geothermal gas out

Dissolved CO2 and H2S

Brine

Figure 6. Schematic diagram of the CarbFix method implemented at the Hellisheiði geothermal power plant [5].

Table 1. List of PhD and MSc students during the CarbFix project.

Student Project title Years

Therese Flaathen Water rock interaction during CO2 sequestration in basalt 2006 – 2009

Alexander Gysi CO2-water-basalt interactions: Reaction path experiments and numerical modelling.

2007 – 2010

Edda Sif Aradóttir Computational study of chemical changes in Icelandic geothermal areas: Coupling chemical reactions into reservoir models.

2007 – 2011

Gabrielle Stockmann

Experimental Study of Basalt Carbonisation 2007 – 2012

Iwona Galeczka Experimental and field studies of basalt-carbon dioxide interaction

2009 – 2013

Snorri Guðbrandsson

Experimental weathering rates of aluminium-silicates. Dissolution of crystalline basalt and plagioclase, and precipitation of aluminium rich secondary minerals

2007 – 2013

Jonas Olsson The formation of carbonate minerals and the mobility of heavy metals during water-CO2-mafic rock interactions

2010 – 2014

Helgi Arnar Alfreðsson

Water-rock interaction during mineral carbonation and volcanic ash weathering

2007 – 2015

Sandra Ösk Snæbjörnsdóttir

Jan Prikyl

Mineral storage of carbon in basaltic rocks dkfljdflkdjfdkjfdkljf

Fluid-rock interaction and H2S and CO2 mineralization in geothermal systems: experiments and geochemical modeling

2012 – 2017

2012 – 2018

Deirdre Clark Mineral storage of carbon in basaltic rocks at elevated temperature. A field and experimental study

2014 – 2019

Mahnaz Rezvani Khalilabad

Characterization of the Hellisheidi-Threngsli CO2 sequestration target aquifer by tracer testing (Masters)

2007 – 2008

Diana Fernandez de la Reguera

Monitoring and verification of geologic CO2 storage using tracer techniques (Masters)

2008 – 2010

Elísabet Vilborg Ragnheiðardóttir

Costs, Profitability and Potential Gains of the CarbFix Program (Masters)

2009 – 2010